The concept of an all-electric ship, which may include the use of electrical means for all power needs in lieu of other means such as mechanical, pneumatic, and hydraulic, is gaining momentum in both U.S. and foreign navies. Versatility in electric power availability will enable new varieties of weapons and ship systems. Some proposed new weapons present especially rigorous power supply requirements. Electro-thermal, chemical, and electromagnetic guns and high-powered laser or microwave directed-energy weapons, for example, require large amounts of power over very short time periods, as do electric rail aircraft launchers (electric catapults), which are technically similar to electromagnetic guns.
Minimizing space and weight requirements onboard naval ships is of prime importance and, as a result, compact gas turbo-generators are an attractive option for generating the electric power needed to energize a ship's electric grid used to power all of the ship's systems. An attractive option would be to utilize a high temperature superconductor (HTS) generator with the turbo-generator to further reduce size and weight of the power source for the ship power grid. However, using a turbo-generator with an HTS generator, results in a relatively low rotational inertia system which is not capable of properly handling the rigorous power requirements of the above described weapon systems and results in disruptive transients imparted on the ship power grid.
With relatively low rotational inertia in the turbo-generator, the torque imposed during the pulsed load has a more significant impact in reducing the rotational speed than with a higher rotational inertia turbo-generator. A drop in rotational speed results in a proportionate drop in frequency, voltage and power from the turbo-generator. To overcome these issues, additional power quality components, such as series inductance or other energy storage means, could be added to the system using the HTS generator. However, they would increase system cost and require additional space. Alternatively, a conventional (non-HTS generator), with increased length and rotational inertia, could be used to overcome the transient problem; however, the additional size and weight of the conventional generator would certainly be a drawback particularly on a ship with constrained bulkhead spacing.